Apparatus for cutting pipes within a well



Feb. 26, 1952 w G SWEETMAN 2,587,244

APPARATUS FOR CUTTING PIPES WITHIN A WELL Filed NOV. 12, 1946 2 SHEETS--SHEET 1 ATTORNEXS 1952 w. e. SWEETMAN APPARATUS FOR CUTTING PIPES WITHIN A WELL 2 SHEETSSHEET 2 Filed Nov. 12, 1946 Has we. SWEETMAN INVENTOR ATTORNEYS Patented Feb. 26, 1952 APPARATUS FOR CUTTING PIPES WITHIN A WELL William G. Sweetman, Houston, Tex., assignor of an interest to I. J. McCullough, Los Angelcs, Calii'., and 0. ll. McCullough, Houston, Tex.,

jointly Application November 12, 1946, Serial No. 709,246

2 Claims. (01. 102-20) This invention relates to a cutting method and apparatus for use within a well, and particularly to a new and novel method and apparatus for cutting objects, such as well pipe and casing, in place in a well by the use of detonating chemicals.

The term cutting, as employed herein, is intended to cover generally directing a cutting jet against a well wall and more specifically against a pipe wall and to include the operations of complete severing of pipe strings as well as the cutting of slots and openings of various sizes and shapes, and the cutting-out of complete tubular segments, commonly termed windows," in pipe walls, and the cutting of other objects, such as drilling tools, in place in a well.

In drilling and production operations connected with wells, such as oil wells, gas wells, water wells, and the like, many occasions arise when one or more of the strings of easing or pipe employed in such wells must be severed, slotted, or windowed at points far below the surface. The cutting of windows or other openings in the wall of a casing string, for example, to provide access to the formations lining the well bore through the wall of the casing liner, without otherwise disturbing the casing liner, requires a degree of exactness and dependability which is dificult to accomplish b present procedures. In windowing or slotting casing, it is normally important that the opening be of the desired dimensions and shape, and that the cutting of the opening be accomplished with a minimum of damage to the surrounding areas of the casing. In some cases it may be desirable to make a series of vertically or peripherally spaced slots in the casing wall, in others, to remove a complete section from the casing or pipe string. Methods heretofore used for cutting all such windows in a well casing or pipe while in place in the well, all require relatively complicated methods and mechanisms which are generally time consuming and expensive and are frequently difiicult to operate for accomplishing the desired purpose.

A principal object of this invention, therefore, is the provision of an efficient and economical method of cutting within a well.

An important object is an efiicient and economical method of cutting well casing, pipe and other objects in place in a well by means of high velocity gases.

Another object is to effect the cutting of well casing and pipe cleanly and sharply by means of high velocity gases generated by the detonation of detonating chemicals.

A further object is to efiect the cutting of objects, such as casing and pipe, within a well, with relatively simple and uncomplicated means.

Further objects will appear from the detailed description taken in conjunction with the accompanying drawings in which will be described and illustrated a number of the embodiments of this invention. It is to be understood, however, that this invention is susceptible of various embodiments within the scope of the appended claims.

In the accompanying drawings:

Fig. 1 is a longitudinal sectional elevation through an embodiment adapted for severing a well pipe from within a well;

Fig. 2 is a cross-sectional view along line 2-2 of Fig. l;

Fig. 3 is a cross-sectional view along line 3-3 of Fig. 1 and having parts broken away to more clearly illustrate the construction of the device;

Fig. 3-A is a partly-sectional elevation of another embodiment adapted for severing a pipe from the exterior thereof;

Fig. 4 is a longitudinal sectional view of another adaptation of this invention for the cutting of longitudinal slots in a, well pipe;

Fig. 5 is a horizontal sectional view along line 55 of Fig. 4;

Fig. 6 is an elevational view, partly in section and partly in perspective, of another embodiment in accordance with this invention adapted for cutting a plurality of radially spaced slots in a well casing;

Fig. 7 is a cross-sectional view along line 7-7 of Fig. 6:

Fig. 8 is an elevational view, partly in section and partly in perspective. of still another embodiment in accordance with this invention for cutting out a window in a well casing;

Fig. 9 is a cross-sectional view taken along line as of Fig. 6;

Fig. 10 is a longitudinal sectional view along line ifi-lfi of Fig. 8; and

Fig. 11 is a detail, partly in section and partly in perspective, of one of the elements incorporated in several of the illustrative embodiments of this invention.

Generally stated and in accordance with illustrative embodiments of this invention, a gaseous penetrating jet is produced by detonating a chemical charge and the resulting gases are con verged to a relatively sharp focus, upon the line of the cut to be made in a well. The term focus is hereinafter employed to describe what is believed to be the theory of action. It is to be understood, however, that this invention is not 3 to be restricted to any theory, which latter is simply advanced for the purpose of supplementing the disclosure hereinafter set forth.

The detonating chemical charge is hollowed and the hollow is of generally concave form. Upon detonation of such a hollowed charge, the resulting gases are directed generally along an axis in a manner well known in the art. However, in accordance with illustrative embodiments of this invention, there is interposed along such axis and in the path of the gases, means which is rupturable by the gases and this means is constructed and arranged to converge the gases to a relatively sharp focus beyond that means. The converging means employed may be of reentrant form, which may correspond to and lie against the hollow of the charge. The cross-section of the converging means may be generally of a conic section, viz., an angle, an ellipse, or a frustrum thereof. This converger has such an angle and is made of such a material and thickness of material, that it will rupture upon detonation of the charge in a manner so as to deform the converger in the direction of the issuing gases in order to converge those gases to a relatively sharp focus; and by variation of the angle of the converger the position of the focus with reference to the charge or the apex of the converger may be varied to obtain a desired focal length for the resulting jet of gases.

The construction heretofore described is such as to not only cause the converging means to converge resulting gases to a relatively sharp focus, but to actually cause penetration of the gases through the convergerso that the resulting jet will pass beyond the converging means rather than have the latter precede it, as in the case of the propelling of a projectile. Moreover, beyond the focus the gases will be maintained in the form of a narrow column foran extended distance beyond the focus.

In the method and apparatus for cutting objects in a well, the jet or column, formed as heretofore described, is directed onto the material to perform its cutting function by penetrating the material to be cut or severed. The cutting is, therefore, primarily performed by the jet and not by a projectile propelled along the travel of the jet; for in actual cutting operation, the converger is preceded by the jet which ruptures this converger.

In the illustrative embodiment of this invention, a closed carrier. dr housing extends from the converging element in the direction of the jet and it is from this housing that the jet is directed. This housing spaces the converger from the closed front and encloses the converger. The housing may also enclose the chemical charge, although that is not necessary. Any suitable initiator may be employed to detonate the charge.

More particularly, the method of this invention may be accomplished by preforming a charge of a detonating chemical of the type described below to a configuration substantially corresponding to the line of the cut to be made in the Well object, and by controllably causing the major proportion of the gases generated by detonation of the charge to be concentrated and focussed relatively sharply on the line of the cut.

Gases traveling at velocities in excess of 1000 meters per second, and which may be at very much higher velocities, are employed for cutting objects in a well in accordance with this invention. Such gases may be generated by the detonation of chemical substances of the type generally designated as detonating explosives which, upon detonation, decompose very rapidly to generate gaseous decomposition products which are capable of attaining extremely high velocities, particularly when suitably controlled and directed in accordance with the method of this invention. Numerous chemicals of this character are available for use in accordance with this invention including such materials as penta-erythritol tetranitrate (PETN), Tetryl, Pentolite, PETN and 50% TNT), trinitrotoluene (TNT), Amatol, Cyclonite, Tetrytol Tetryl and 40% TNT), and many others well known to those familiar with such detonating chemicals.

By way of an example, a detonating chemical composition comprising a mixture of PETN and TNT, when used in accordance with this invention, will develop a wave of gases which travel at velocities of over 10,000 meters per second at 200,000 atmosphere of pressure and approximately 3900 degrees centigrade absolute temperature. It is believed that the temperature of the gases is a relatively unimportant factor in the cutting action of the gases, since at the extremely high velocities involved. the time interval involved in making a cut of any desired depth is so short as to render the temperature effect relatively negligible.

The detonating chemicals may be employed in cast or compressed solid form, but are employed preferably in the form of plastic or gelatinous masses which may be readily molded to the desired form for use in accordance with this invention, and may be used individually or as blends of two or more of them in suitable proportions, and may include suitable detonable plasticizers. Only relatively small quantitie of detonating chemicals, when used in accordance with this invention, are required to accomplish the complete severing or windowing of easing or pipe, or the cutting of other objects in a well and will produce cuts which are relatively clean and sharp and with minimum damage to areas of the casing or pipe adjacent to the cut.

The concentration, converging and focussing of the generated gases is efiected, as above described, by applying to a face of the preformed charge directed toward the object to be cut, a concave control member, which has been termed a "converger, and which is of predetermined form which is preferably angular in cross-section but which may be arcuate, or a combination of both forms, as described above.

The size of the angle or arc enclosed by the converger determines the shape of the jet or beam of gases which will be directed toward the object to be cut and distance from the inner end of the converger at which the gases will be brought to the desired focus, and this, in turn, will determine the optimum spacing of the charge from the object to be cut. The size of this angle will usually be less than Furthermore, the shape of the converger will also determine the optimum distance over which the gases may be maintained in effective jet or beam form, and therefore, the depth of the out which may be made by the gases. Thus, for a given angle in the converger, the gases will be caused to come to a focus at a predetermined distance from the base or apex of the converger and will travel a predetermined distance in a relatively concentrated beam or jet before scattering or dissipation of the gases. Once the gases begin to scatter or diverge from the focal point or line, the effecaeemce tiveness of the cutting action is reduced extremely rapidly. Thus, when it is desired to cut through a steel casing, for example, with minimum penetration of the earth formations behind the casing, by selecting a suitable relatively wide angle for the converger, the explosive gases may be caused to be focussed in suitable cutting concentration on the face of the casing and to retain their effective narrow jet or beam form for a distance suflicient only to penetrate through the casing wall, and to then scatter or diverge sharply immediately after passing the rear face of the casing wall, with an immediate loss of penetrating power such that the cutting action of the gases on any material immediately behind the casin will be relatively negligible. On the other hand, by selecting a different and narrower angle for the converger, the gases can be brought to a focus and caused to travel in narrow beam form of cutting concentration and velocity a greater distance than the thickness of the casing wall, so as to pass through the casing wall and penetrate a predetermined distance into the formations behind it.

In many respects, the principles involved in the shaping of the converger to bring the gases to a focus at a predetermined distance from the end of the charge and to determine the shape of the jet or beam of gases, are quite analogous in function and in the mathematical calculations I involved to well known optical principles, in that the converger may be likened to a concave mirror or lens, and the actions of the gases passing through the converger from the charge may be made to correspond closely in many respects to the actions of a beam of light rays passing through a concave lens or reflected from a concave mirror. Accordingly, in view of the analogous relationship, optical terms such as focus, focal length, beam, etc., are employed in connection with the description of this invention, and their meaning will, therefore, be clearly evident as so employed.

The convergers employed in accordance with this invention are preferably constructed of thin metal, such as steel, brass, copper and the like, or of glass or rigid plastic composition which have been preformed or molded to the desired shape. The wall thickness of the convergers is a function of the depth of the cut to be made, that is,

the distance from the focus of the beam through the object to be cut, andawill, therefore, be varied in accordance with the requirements of each use. In most circumstances the wall thickness of the converger will range from less than 1% to about of the depth of the cut. It is important to note that the convergers employed in accordance with this invention are not in any sense projectiles, and are normally disintegrated or pierced by the the gases leaving the charge without forming, or functioning as, projectiles in the ordinary sense of this word.

In order to assure the proper development of an eifective cutting beam of gases, the gases leaving the converger should preferably be guarded from interference by any extraneous solid or liquid matter until the gases attain the desired focussed form, for until the gases reach their point or line of focus, the interposition of any extraneous solid or liquid matter in their paths will deflect and dissipate the gases so as to prevent their concentration, converging and focussing into an efiective cutting beam. The guarding of the gases leaving the converger is preferably accomplished by enclosing the converger within a shielding housing, constructed of any suitable metal or rigid plastic composition, extending in the direction of the desired path of the gases and terminating at a distance from the end of the converger which is substantially the predetermined point or line of focus of the beam of gases. The outer end of the shielding housing may be closed, if necessary, to exclude any extraneous liquid or solid matter from the interior thereof. Since this end closure will be at substantially the focus of the beam of gases, it can no longer interfere with the effective cuttin action of the beam and will be cut thereby as, in efiect, a portion of the object against which the gases are primarily directed.

Referring now to the drawings and first to Figs. 1, 2 and 3, there is illustrated an embodiment, in accordance with this invention, for severing a well casing or other pipe 20. An annularly shaped cutting unit, designated generally by the numeral 2i, and constructed generally of two semi-circular segments, is disposed in a complementary circular slot 22 cut horizontally into the periphery of a generally cylindrical body 23, which may be constructed of steel or other metal, or of solid plastic or other suitable rigid composition material which will serve as a suitable holder for the cutting unit. The diameter of body 23 is generally made somewhat less than the internal diameter of casing 20 so that it may pass readily therethrough. An axial passageway 24 extends entirely through body 23 and at its upper end, registers with the bore 25 of a tubular stem 26 which is threadedly connected to the upper end of body 23. A bail 21 is attached to the upper end of stem 26 by means of which the device may be suspended on a lowering line 28 connected to the bail.

A generally tubular chamber 29, radially spaced from passageway 24, extends vertically into body 23 from the upper endthereof into communication with slot 22 and is arranged to contain a detonating fuse member 30, of generally conventional form. The upper end of chamber 29 is closed by means of a suitable threaded plug 3! which is provided with a hydrostatically sealed opening 32 through which a pair of electrical leads 33, connected to fuse member 30, extend into the interior of casing 20, whence they lead to any suitable form of electrical firing device (not shown) which is adapted to fire fuse member 30. The outer end of slot 22, in which cutting unit 2! is seated, is closed by means of an annular sleeve 3% which is arranged to fit closely about the periphery of body 23 and form a fluidtight closure for slot 22. It will be understood that the sleeve 34 is not perforated as shown in Fig. 1, but later becomes perforated by the cutting gases.

Cutting unit 20 (see also Fig. 11) comprises a pair of spaced, parallel, ring-shaped walls 353 5, which may be constructed of thin sheet steel or other metal, or of rigid plastic or glass composition.

Mounted between walls 35-35 is a converger 36, which likewise may be constructed of thin metal, plastic or glass, and which is generally V-shaped in cross-section and annular in plan view, having the opening of the V directed toward the line of the cut to be made in casing 20. Converger 36 is spaced from the outer ends of container walls 35-35 a pre-determined distance depending upon the angle of the converger, as above described. The desired spacing may be effected, as illustrated, by means of a pair of thin parallel extensions 3'|--3'|, which extend from the edges of converger 36, and which fit closely against the adjacent inner faces of walls 35-35 and terminate flush with the outer ends thereof and against the inner surface of sleeve 34.

It will be understood, of course, that extensions 31-.31 may be eliminated, if desired, and converger 36 fixed in the desired position between walls 3535 by welding, soldering or otherwise suitably attaching the edges of the converger to walls 35--35.

The inner portion of cutting unit behind converger 36 is packed with a mass of a suitable detonating chemical 38, of the type described above, so that the outer face of the mass assumes the shape of the converger. The upper one of walls is provided with an opening 39 (Fig. 3) which registers with the lower end of chamber 29 and through which fuse member 3|) extends into the mass of detonating chemical 38.

To sever casing 20, the device, assembled as described above, is lowered by means of lowering line 28 to the desired position in the casing opposite the point at which the cut is to be made and chemical charge 38 is detonated. The high velocity gases generated by detonation of the chemical charge rupture converger 36 and are converged thereby to a focus on the inner face of sleeve 34 in the form of a thin annular beam,

as indicated by the arrows in Figs. 1 and 2. This beam cuts through sleeve 34 and through the wall of casing 20 and produces a relatively narrow cut entirely around the periphery of the casing and cleanly severs'the casing.

As previously described, by suitable selection of the angle of the converger, the gases may be brought to a focus and maintained in a narrow column of cutting concentration for a distance suflicient only to cut through the casing wall, and to then diverge so as to eiTect minimum penetration of the surrounding earth formations.

This method of controlling the depth of the cut is particularly useful when the above-described embodiment is applied to the cutting of the inner one of a pair of concentric pipes, without injuring the outer pipe, as when applied, for example, to the cutting of a string of drill pipe inside a surrounding casing. D

As an example of one specific application of the above-described embodiment to the severing, while in place in a well, of five and one-half inch casing, having a wall thickness of approximately one-half inch, cutting unit 2| will comprise an annulus having an outside diameter of 4.25 inches, an inside diameter of 1.844 inches and one-half inch wide between side walls 35- 35. Converger 36.will have an angle of '72 degrees and be constructed of mild steel thirtysix thousands (0.036) inch thick, and the outer edges thereof will be spaced approximately threeeighths inch from the inner face of sleeve 34. Approximately 90 grams of Pentolite will be employed to sever the casing.

Cutting of easing or other pipe strings in a well may be easily accomplished by the embodiment described, whether or not well fluids or drilling mud is present in the well. The provision of the axial passageway 24 and hollow stem 26 permits the cutting tool to be lowered through a column of such fluid without difficulty. Weight sufllcient to sink the tool through such fluids may be supplied by making body 23 of steel or by attaching any suitable weighting member to the cutting tool. The presence of any well fluid or drilling mud in the narrow annular space between the outside of body 23 and the inner wall of casing 20 will not interfere with the eflicient cutting action of the developed jet of gases. so long as it is excluded from the area between the outer face of converger 36 and the point at which the generated gases come to a focus, in this case, at about the inner face of sleeve 34.

Fig. 3-A illustrates another embodiment in accordance with this invention applied to the cutting of a generally cylindrical object within a well by directing the cutting jet against the exterior of the object. The invention is illustratively applied to the cutting of a tubing 20a inside well casing 20. It will be understood that tubing 20a may be a conventional drill pipe or drill rod, as used in rotary drilling, or even a conventional wire line, as commonly used in cable tool drilling. It will be further understood that this embodiment may be applied, as illustrated, in the absence of a well casing, the presence of the well casing in the well bore being unessential to the successful accomplishment of this particular application of the invention.

As illustrated, a ring-shaped cutting unit 2|a surrounds the exterior of tubing 20a and is substantially identical in form and construction to cutting unit 2| of Fig. 1, except that cutting unit 2|a has its converger 36a facing inwardly instead of outwardly as in the case of converger 36 of Fig. 1. Cutting unit 2|a is attached to the lower end of a tubular guide sleeve 2|b.

which surrounds tubing 20a and a lowering line 28a is connected to the sleeve 2|b for lowering the cutting unit to the desired position in the well along tubing 20a. A conventional detonating means 30a is inserted into contact with the detonating chemical 38a in the cutting unit and is connected by electrical leads 33a to a suitable electrical initiator (not shown).

With this embodiment tubing 20a can be cleanly severed by the application of the cutting jet, developed by cutting unit 2|a in a manner similar to that previously described, to the exterior of the tubing to produce a clean annular cut entirely around the periphery of the pipe.

A standard type well tubing three and one-half (3.5) inches in external diameter and of about three-tenths (0.3) inch wall thickness may be severed by employing about grams of Pentolite, shaped, as illustrated, into an annulus about three-eighths inch thick. Converger 36a is constructed of mild steel approximately thirtyfour thousandths (0.034) inch thick and has an angle of about 72 degrees. The inner end of the converger will be spaced approximately threeeighths inch from the exterior of tubing 20a Figs. 4, 5 and 11 illustrate another embodiment in accordance with this invention which is useful for cutting a single longitudinal slot in a well casing in place in a well. In this embodiment, a cutting unit, designated generally by the numeral 40, and having a length substantially equal to thelength of the slot to be cut in a casing 4|, is closely enclosed within a closed tubular sheet metal housing 42, of smaller diameter than casing 4|. Bow spring members 43 are arranged on the outside of housing 42 in alignment with the rear longitudinal edge of cutting unit 40 and bears against the opposite side of the wall of casing 4|, whereby the forward edge of cutting unit 40, in the enclosing housing, is positioned closely adjacent the portion of the wall of casing 4| in which the slot 9 is to be cut. Housing 42 is suspended from a lowering line 44, to which a suitable weighting member 45 may be attached when required to assure the downward movement of the housing in the casing to the desired cutting position.

Cutting unit 46 comprises a narrow rectangular container, having spaced parallel sidewalls 46-43 constructed of thin sheet metal. A front wall 41 closes one of the longitudinal edges of the container and the other longitudinal edge ,is closed by means of a friction cover 48. The ends of container are closed by end walls 49-49. Front wall 41, cover 48 and end walls 49 may be eliminated, if desired, particularly, when housing 42 is made fluid-tight. A V-shaped converger 50 is disposed within the container between the side walls thereof and is spaced from front wall 41, or from the front edges of side walls 46-46, a pre-determined distance, depending upon the angle of the converger, by means of extensions |-5| as described above. The length of converger 50 is substantially equal to the length of the cut to be made. The interior of the container behind converger 50 is packed with a mass of a suitable detonating chemical 52 of the type described above. A suitable initiator 53 is inserted in one end of the container and is connected by leads 54 to a suitable firing device (not shown) and pass through a suitable hydro-statically sealed opening 55 in the upper end of housing 42.

This embodiment is employed to cut a slot longitudinally in the wall of easing 4| by lowering container 42 with cutting unit 40 to the desired point within the casing by means of lowering line 44 and detonating chemical charge 52. The gases generated by detonation of the chemical charge will rupture converger 5n and will be focussed thereby at approximately the inner face of front wall 41 in the form of an elongated narrow beam which will then cut through front wall '41, the wall of hous ng 42 and the adjacent wall of casing 4|, to produce a long narrow cut substantially equal in len th to the cutting unit.

As previously described by selection of the proper angle for converger 5 6, the focussed beam of gases will be maintained in narrow column form of cutting concentration for a distance sufficient only to penetrate through the casing wall and to then scatter quickly so as to have relatively negligible cutting efiect on the surrounding earth formations. On the other hand by the selection of a narrower angle for the conver er, and correspondin ly changing the spacing of the converger from the casing wall. the beam of gases may be caused to penetrate through t e casing wall and cut slots of the desired depth in the surrounding earth formations.

It will be understood that this embodiment may be similarly emplo ed, in the absence of cas ng. for directly cutting slots in the earth formations l ning a well bore.

By way of example, to cut a slot three feet lon in a casing three-quarters of an inch thick, cutting unit 40 will be made about three feet long with side walls 46-46 s aced about onehalf inch apart. Converger 50 constructed of mild steel about thirty-six thousandths (.036) inch thick, will also be about three feet long and will have an angle of '72 de rees, and will be s aced about three-eighths inch from the inner face of front wall 41. Approximately 400 grams of Pentolite will be used to generate the cutting gases.

Where it is desired to have the cutting jet penetrate into the surrounding earth formations to t a depth of one foot behind the casing, the same, set-up will be employed but converger will be changed to an angle of about degrees, a thickness of about forty thousandths (.040) of an inch and will be spaced about five-eighths inch from the inner face of front wall 41. Side walls 46-46 will be spaced approximately three-quarters of an inch apart and approximately 684 grams of Pentolite will be employed for this operation.

Figs. 6 and 7 illustrate a further embodiment for cutting a series of angularly spaced slots in casing 4|. In this embodiment, a plurality of cutting units 40 (three, in the illustrative embodiment) are symmetrically arranged within housing 42, which, in this case, is only slightly smaller in diameter than the bore of casing 4|, so as to have only sufficient clearance for movement therethrough. The structural features of each of the cutting units 46 are substantially identical with those previously described. The opposite ends of the cutting units 4|] are attached to end plates 54a which serve to fix the relative positions of the cutting units. Each of the cutting units is provided with a suitable detonator fuse (not shown), which are suitably connected to an electrical conductor 55a leading to a firing device (not shown). A lowering line 56 is employed to lower the cutting tool to the desired position in the casing.

With this device, detonation of the chemical charge contained in the several cutting units will produce a corresponding plurality of angularly spaced longitudinal slots in the wall of the easing or in the surrounding formations, or in both, in the manner previously described in connection with the preceding embodiment.

Figs. 8, 9 and 10 illustrate still another embodiment in accordance with this invention which is particularly useful for cutting a window in a well casing such as casing 4|. By window in this connection is meant the removal of a complete tubular section from the casing string to provide access to the surrounding earth formations.

In this embodiment, a plurality of vertically spaced, annular cutting units, corresponding to cutting unit 2| of the embodiment illustrated in Fig. 1, and a plurality of longitudinally extending angularly spaced cutting units, corresponding to cutting units 40 of Figs. 4 and 6, are combined to form a generally tubular grid, designated generally by the numeral 60, as illustrated particularly in Fig. 8. Grid 66 is enclosed within a closed container 51 which is suspended from a lowering cable 58, and one or more detonating fuse members (not shown) are inserted at one or more points in the grid and suitably inter-connected to an electrical conductor 59 which leads to a firing device (not shown).

Upon detonation of the chemical charge in each of the several cutting units (the detonation occurring practically simultaneously throughout the grid) a plurality of intersecting circumferential and longitudinal cuts will be made in the pipe wall, corresponding to the configuration of the grid. The circumferential cuts made by the uppermost and lowermost ones of the cutting units 2| will define the upper. and lower edges of the desired window. The intersecting cuts made by the other units in the intervening portion of the casing wall will serve to cut up this section of the easing into relatively small pieces which can then be removed very readily from the well. With this arrangement, therefore, a single cutting operation will suffice to cut a window of any desired size in a well casing and the cutting will be accomplished in such a manner as to permit easy removal from the well of the entire section of casing which it is desired to eliminate.

A similar grid configuration of cutting units, in which the cutting jets are directed downwardly instead of laterally, may be employed for cut- .ting into small pieces, tools which may-have been lost or stuck in the bottom of a well, and which are otherwise very diflicult to remove'from the well by conventional methods.

From the foregoing, it will be understood that cuts of any desired configuration and arrangement may be made in a well, by employing a charge of detonating chemicals which has been preformed to the configuration of the cut to be made, and by employing an angular converger of similar lineal configuration to converge and focus the generated gases into a narrow beam of very high velocity and of generally corresponding configuration, and by directing the focussed beam upon the surface to be cut.

The apparatus employed is of relatively simple and low cost construction, and the desired cutting operation may be performed relatively quickly and efficiently and at a minimum of expense.

It will be understood that various alterations and modifications may be made in the details of this invention without departing from the scope of the appended claims but within the spirit of this invention.

What I claim and desire to secure by Letters Patent is:

1. An apparatus for severing pipe in a well. comprising, a massive cylindrical body member for insertion into the pipe, said body member having a radially directed circumferential recess therein extending interiorly of the body to a point intermediate the exterior of the body and the longitudinal axis thereof to provide a charge-backing support, an annular high explosive charge in said recess seated against said charge-backing support, an annular hollow of angular cross section formed in the outer periphery of said charge and directed radially outwardly, an annular liner conforming in shape to and seated in said hollow, a pair of substantially parallel spaced-apart annular spacer elements connected to and extending radially outwardly from the outer edges of said liner, and a circumi'erentially extending pressure sealing wall bridging the outer ends of said spacer ele' ments and closing said recess.

2. An apparatus for severing pipe in a well comprising, a rigid cylindrical body member fol insertion into the pipe, said body member having a radially directed circumferential recess therein extending interiorly of the body to a point intermediate the exterior of the body and the longitudinal axis thereof to provide a chargebacking support, an annular high explosive charge in said recess seated against said chargebacking support, an annular hollow of angular cross section formed in the outer periphery of said charge and directed radially outwardly, an annular liner conforming in shape to and seated in said hollow, a pair of substantially parallel spaced-apart annular spacer elements connected to and extending radially outwardly from the outer edges of said liner, a circumferentially extending pressure sealing wall bridging the outer ends of said spacer elements and closing said recess, and a detonating means mounted on said body member and extending into detonating contact with said charge at a point spaced radially inwardly from the apex end of said angular hollow.

WILLIAM G. SWEETMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,144,208 Van Meter Jan. 17, 1939 2,399,211 Davis Apr. 30, 1946 2,407,093 Mohaupt Sept. 3, 1946 2,415,814 Davis Feb. 18, 1947 2,436,036 Defenbaugh Feb. 17, 1948 2,494,256 Muskat Jan. 10, 1950 

